test/wcc/data: grow the declarative compiler corpus to 1,224 fixtures

The r-prefixed waves absorb the runtime, reject, and byte-compare rows
of the migrated native carriers; each fixture is one directory with one
case.ww and a //ww:error, //ww:compile, //ww:run, or //ww:run-exit
directive covering both frontends.

test/wcc/data/r79_tuple_sret_three_f64/case.ww

@@ -0,0 +1,3 @@
+//ww:compile
+package main;
+export fn f(x: f64, y: f64, z: f64) (f64, f64, f64) = { return (x, y, z); };